We hypothesize that polymorphonuclear leukocyte (PMN) margination (sequestration) in the lung is an important early event in the development of the acute respiratory distress syndrome (ARDS) and that this event is regulated by the activation and expression of adhesion molecules. The overall objective of this proposal is to predict which high risk patients will develop ARDS before they enter a respiratory distress stage. We will take advantage of a widely used scintigraphic imaging procedure, 111-Indium labeled autologous white blood cells in an attempt to measure margination in various organs, particularly lung, during the progressive development of ARDS. Further, we will also determine if changes in adhesion molecule expression on PMN correlate with the 111-Indium imaging analysis, clinical status, or if adhesion molecule expression itself can be used as a predictive tool. The approach involves the recruitment of a select group of patients at high risk for developing ARDS.